1. Field of the Invention
This invention relates to an asphalt foam, particularly, an asphalt foam excellent in its workability and flame retardancy, and a method of producing the same.
2. Description of the Prior Art
A foam having open cells, e.g., urethane foam, if impregnated with a molten asphalt, is enabled to exhibit a water repellency and a moderate restoring force. The asphalt-impregnated foam, which is called an asphalt foam, is widely used as, for example, a joint filler. Recently, the asphalt foam has also been found to be excellent in its sound absorbing and shielding properties and exhibit a high vibration resistance, leading to an additional use of the asphalt foam as, for example, a vehicle floor material requiring a sound-proof and vibration resistance properties.
In the conventional asphalt foam, however, the impregnated asphalt is simply attached to the cell wall of the foam, giving rise to serious problems. For example, the asphalt oozes onto the foam surface in the punching step of the asphalt foam, making the foam surface sticky. Also, another material is stained with the oozing asphalt. What should also be noted is that the viscosity of the molten asphalt is changed depending on the heating conditions, resulting in failure to have the foam uniformly impregnated with the molten asphalt.